Tracking Cancer

March 23, 2009 9:15:37 AM PDT
Colorectal cancer refers to cancer that starts either in the colon or the rectum. They are often joined by name because they have many common features. Colon cancer forms in the tissues of the colon, the longest part of the large intestine. Most cases of colon cancer are adenocarcinomas, or cancers that arise in cells that make and release mucus and other bodily fluids. Rectal cancer forms in the rectum, the last several inches of the large intestine. The American Cancer Society says excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in the United States. National Cancer Institute estimates show 108,070 cases of colon cancer, 40,740 cases of rectal cancer and 49,960 cases of combined colon and rectal cancer were predicted to occur in the United States in 2008. TREATMENT: As is the case for most other cancers, the four main types of treatment are surgery, radiation therapy, chemotherapy and targeted therapies, which are also called monoclonal antibodies. The main treatment for both colon and rectal cancers is surgery. For colon cancer, a colectomy is performed. This usually involves removing the cancer and part of the colon, as well as nearby lymph nodes. The two ends of the colon are then sewn back together. For rectal cancer, the type and invasiveness of the surgery depends on the location and size of the cancer. Some rectal surgeries can be done without cutting into the skin, but others require operating on the colon and other nearby organs as well.

SCREENING THE BLOOD FOR CANCER: Almost all cancers form through the mutation of genes that control the growth of cells. Because of this, as cancers grow, they shed fragments of DNA into the bloodstream. A new test measures levels of DNA from tumors that end up in the bloodstream. Researchers say the test can not only detect the presence of a tumor; it can also track its progress. A study assessing the test involved 18 patients with colorectal cancer. To test the patients, researchers first identified the mutations present in each patient's cancer. They then used a method called BEAMing to search for related mutant tumor DNA in the patients' plasma. In all 18 patients, the same mutations detected in their tissue were found in their plasma. The test also measures the level of tumor DNA circulating in the blood. The higher the level of mutant DNA, the more advanced the cancer.

Doctors hope the test will also be able to predict who is susceptible to cancer and, when a patient gets cancer, if it will recur. "We want to say with as much certainty as we can who will recur and who won't recur, because if we find out with good certainty who will recur, those patients are the ones to whom we recommend chemotherapy," Luis Diaz, M.D., an oncologist at the Johns Hopkins Kimmel Cancer Center in Baltimore, Md., told Ivanhoe. Another test that shows promise for predicting the responsiveness of colorectal cancer patients to treatment is microRNA expression. A recent JAMA study shows high levels of the microRNA called miR-21 may predict poor patient survival.


Johns Hopkins Kimmel Cancer Center
Valerie Mehl, Public Relations
(410) 955-1287